15666: Change password of an account with an email used more than once

Description

If you add a new user with a E-Mailadress already in use (SuperAdministrator in my case) and change the password of that new account, you'll get an error that the password cannot be changed. After changing the emailadress you can change the password.

The sideeffect is that LimeSurvey is now warning that the first account (which is the using the emailadress all the time) has never changed the default password (which isn't that case).